Supported phospholipid monolayers. The molecular structure investigated by vibrational sum frequency spectroscopy

Jonathan F.D. Liljeblad, Vincent Bulone, Mark W. Rutland, C. Magnus Johnson

Research output: Contribution to journalArticlepeer-review

39 Citations (Scopus)

Abstract

The molecular structure, packing properties, and hydrating water of Langmuir-Blodgett monolayers of the phospholipids 1,2-distearoyl-sn-glyerco- phosphatidylcholine (DSPC, 18:0 PC), its deuterated analogue (18:0 PC-d83), and 1,2-distearoyl-sn-glyerco-phosphatidylserine (DSPC, 18:0 PS) deposited on planar calcium fluoride (CaF2) substrates have been investigated using the surface-specific nonlinear optical technique vibrational sum frequency spectroscopy (VSFS). Compression isotherms were recorded before the deposition of the monolayers at a surface pressure of 35 mN/m, mimicking the conditions of biological cell membranes. The CH and CD stretch regions, the water region, and the lower wavenumber region, containing phosphate, ester, carboxylate, and amine signals, thus partly covering the fingerprint region, were probed to obtain a complete map of the molecules. The data indicate that all deposited monolayers formed a well-ordered and stable film, and probing the water region revealed significant differences in hydration for the different headgroups. In addition, the tilt angle of the aliphatic chains relative to the surface normal was estimated to be approximately 4° to 10° based on orientational analysis using the antisymmetric methyl stretching vibration. Orientational analysis of the ester C=O groups was also performed, and the result was consistent with the estimated tilt angle of the aliphatic chains.

Original languageEnglish
Pages (from-to)10617-10629
Number of pages13
JournalJournal of Physical Chemistry C
Volume115
Issue number21
DOIs
Publication statusPublished - 2 Jun 2011
Externally publishedYes

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